Many types of sensors are known and used in a broad variety of industrial and consumer product applications. Motion sensors are used for detecting, tracking and signaling the motion of an object, preferably detecting the motion in different dimensions of space. There are a number of designs that have been implemented, for example the use of a mounted pendulum, mercury switch, Hall effect detection, and the use of an electrically conductive ball within a housing. See U.S. Pat. Nos. 4,101,093; 4,196,492; 4,584,569; 6,087,936. Pendulum type systems have a number of shortcomings. Primarily, a pendulum system requires a steady surface for mounting and calibration. Additionally, Mercury tilt switches have fallen into disfavor because of environmental concern. Hall effect sensors can be complicated in design and expensive to manufacturing. Additionally, many of the prior art motion sensors are of a large size making it necessary to operate as a separate component from the product it is used with, requiring the need to send a motion signal from the sensor to another device in order for the motion signal to be detected.
Motion sensors designs have also been conceived that can be mounted on a printed circuit board. For example U.S. Pat. No. 3,742,478 discloses a motion sensitive switch, which includes a housing mounted on a circuit board and a steel ball positioned under the housing and rolling freely over three separate circuits traced on the surface of the printed circuit board. As the steel ball rolls over the circuits it makes and breaks the circuits, triggering an alarm event. There is a limitation in this type of design in that it can be overly sensitive to vibration causing undesirable triggering of a motion event, such as a concussion from a door knock, passing vehicle, or heavy construction work. Additionally, the sensor cannot provide any indication of the direction of movement of the sensor.
U.S. Pat. No. 6,339,199, issue to Chou, discloses a tilt sensor that is mounted to the surface of a printed circuit board. A central electrical contact on the surface of the printed circuit board defines a rolling area where a conductive ball may roll. There is an electrically conductive housing that encloses the conductive ball over the central contact area. The housing is also associated with a second contact area. When the sensor is tilted the ball will roll and make contact with the interior surface of the housing and the central contact area, closing a circuit and triggering a motion signal. The Chou design is limited in that it only detects motion itself, and it does not provide any indication of directionality of movement in three dimensional spaces.
U.S. Pat. No. 4,980,575, issued to Schenkel, discloses a motion sensor configuration with a first and second conductive housing. Each conductive housing contains a metal ball and is coupled together by an insulative material. The insulative material has passage that allows movement of the metal ball between each conductive housing, such that when movement occurs the metal balls will shift to make contact with the surface of the other metal ball which is in contact with the other housing elements and closing a circuit between the first and second housings. The Schenkel design is limited in that it can only detected motion in a single plane of movement. It is further limited in that the design is complicated, requiring a number of sensor components. Further, it is difficult to manufacture and expensive to build.
Therefore, there remains a need for a motion sensor that can detect motions in three dimensions, is easily manufactured at low cost and that does not required to be mounted on a platform or special apparatus.